This invention relates to a winding unit for intermittently winding a web such as a tape.
This type of winding unit is used to wind a web fed from an intermittently operating processing stage in synchronization with the operating pitch of the processing stage. For example, it is used to wind a cover tape (also called top tape) which has transported electronic parts such as semiconductor chips in pockets of the tape, or to take up a cleaner sheet used to clean the fixing unit of a copier or a printer.
FIGS. 24 and 25 show a winding unit used to wind a cover tape 60 after it has transported semiconductors. A reel 61 of the winding unit includes a support reel 62 having a reel boss portion 62xe2x80x2 and a detachable reel 78 mounted on the reel boss portion 62xe2x80x2 so as to be not rotatable relative to the reel boss portion. The cover tape 60 is wound around the detachable reel 78. This winding unit has a one-way clutch 63 for driving and a one-way clutch 64 for braking mounted in an inner peripheral surface of a reel boss portion 62xe2x80x2. The one-way clutch 63 for driving is mounted on a stepped fixed shaft 67 through a rotary sleeve 66 having a pivoting lever 65, while the one-way clutch 64 for braking is directly mounted on the fixed shaft 67.
The fixed shaft 67 is fixed by a bolts 69 to a bracket 68, which is fixed to a base 79 (FIG. 24) by bolts 80. Thus the rotary sleeve 66 is prevented from coming off the shaft 67 by the bracket 68.
The pivoting lever 65 is intermittently pivoted by a predetermined angle (shown by arrow A in FIG. 24) in synchronization with the pitch of supply of semiconductor chips. At this time, the one-way clutch 63 for driving locks the reel boss portion 62xe2x80x2 and the rotary sleeve 66 together, and the support reel 62 rotates a predetermined angle together with the rotary sleeve 66 to wind the cover tape 60 around the reel 61. When a predetermined length of cover tape 60 has been wound, the pivoting lever 65 is returned to the original position by a coil spring 70. At this time, the one-way clutch 64 for braking locks the reel boss portion 62xe2x80x2 and the fixed shaft, 67 together, so that only the pivoting lever 65 and the rotary sleeve 66 return to the original positions.
The one-way clutches 63 and 64 have on the inner peripheral surfaces of their outer rings 71 and 72 a plurality of cam surfaces inclined in the circumferential direction. At positions opposite to the respective cam surfaces, rollers 73 and 74 are mounted. The rollers 73 and 74 are biased by springs 75 and 76, respectively, in such directions that they are locked by the cam surfaces. The one-way clutches 63 and 64 are axially separated from each other by a shoulder 77 formed on the inner peripheral surface of the reel boss portion 62xe2x80x2 so as not to interfere with each other.
With this winding unit, when the reel 61 becomes full of the wound cover tape 60, it is necessary to dismount the detachable reel 78 from the support reel 62 for replacement.
But since the support reel 62 is braked by the one-way clutch 63 for braking and cannot turn in reverse, tension during winding still acts on the cover tape 60. This makes it difficult to dismount the detachable reel 78.
An object of this invention is to provide a winding unit in which during replacement of the reel 78, the reel can be rotated in reverse direction so that the tension in the cover tape 60 can be released.
According to this invention, there is provided a winding unit for winding a web, the winding unit comprising a fixed shaft, a rotary sleeve having a lever and rotatably mounted on the fixed shaft, a support reel having a reel boss portion, a reel detachably mounted on the reel boss portion, a one-way clutch for driving and a one-way clutch for braking each having an outer ring formed with a plurality of circumferentially inclined cam surfaces on an inner peripheral surface thereof, rolling elements mounted at positions opposing the respective cam surfaces, and springs for biasing the rolling elements in such directions as to be locked by the cam surfaces, the one-way clutches being mounted in the reel boss portion, the one-way clutch for driving being mounted on the fixed shaft through the rotary sleeve, the one-way clutch for braking being mounted on the fixed shaft, the reel being intermittently rotated by pivoting the pivoting lever to wind the web on the reel, a torque limiter being provided between the outer ring and the reel boss portion to shut off transmission to the outer ring of a turning torque in the unwinding direction applied to the reel boss portion.
With this arrangement, either during the intermittent web winding periods or during intermittent rest periods, the torque limiter assures winding without producing any slip, and the web maintains a constant tension due to the function of the one-way clutch for braking. When necessity of releasing the tension in the web arises e.g. during replacement of the reel, by forcibly turning the reel in the unwinding direction, the reel will turn while slipping relative to the outer ring to release the tension in the web.
More specifically the torque limiter is set so as to have a sufficiently large winding torque value for the transmission of torque in the winding direction from the outer ring to the reel boss portion and to have a predetermined unwinding torque value for the transmission of a torque in the unwinding direction from the reel boss portion to the outer ring. When the reel boss portion is forcibly turned with a torque exceeding such an unwinding torque value, slip occurs.
As a further specific structure, the torque limiter is a spring type torque limiter comprising a torque limiter ring mounted on an outer peripheral surface of the outer ring, and a coil spring mounted on an outer peripheral surface of the torque limiter ring with a predetermined binding force, the coil spring has one end thereof engaging the reel boss portion, the coil spring being adapted to lock when the torque limiter ring rotates in the winding direction so that the binding force increases, and to have a predetermined unwinding torque value when the reel boss portion rotates in the unwinding direction so that the binding force decreases.
A restraining means for the coil spring may be provided on the reel boss portion to prevent one end of the coil spring from moving in the circumferential direction. With this arrangement, when winding around the reel is performed by pivoting the pivoting lever, movement of the coil spring relative to the reel boss portion is prevented by the restraining means, so that the pivoting angles of the pivoting lever and the reel coincide with each other.
The coil spring may have the other end thereof engaging a lid member fitted in the end of the torque limiter ring.
The torque limiter may be a press-in type torque limiter in which the torque limiter ring is pressed in the reel boss portion.
Also, there is provided a structure wherein the torque limiter is a cam type torque limiter comprising a torque limiter ring pressed in the reel boss portion, cam recesses formed in one of the torque limiter ring and the reel boss portion, rolling elements housed in pockets formed in the other thereof so as to oppose the cam recesses, and resilient members each housed in the respective pocket for biasing the rolling elements toward the cam recesses.
As a further specific structure of the cam type torque limiter, there is also provided a structure wherein the torque limiter ring has a rolling element retaining portion on a radially outer side thereof and a resilient member retaining portion on a radially inner side thereof, the rolling element retaining portion being formed with a plurality of pockets at angular spacings so as to radially extend therethrough, the rolling elements being housed in the respective pockets and biased from a single resilient member housed in the resilient member retaining portion. With this arrangement, since the resilient members are formed of a single member, the number of parts decreases.